In an optical communications network, an optical signal is modulated with digital information and transmitted over a length of optical fiber from a source location to a destination location. An M×N optical switch module allows switching of optical signals from any one of M optical fibers to any one of N optical fibers spanning between various locations of the network. A multicasting M×N optical switch allows one to switch optical signals from one optical fiber to not one but, simultaneously, to a plurality of optical fibers, or to switch optical signals from a plurality of input optical fibers to a plurality of output optical fibers, such that optical signals in any of the input optical fibers can be multicast into non-overlapping subsets of the plurality of the output optical fibers.
One drawback of optical switches of the prior art is a large number of optical waveguides that need to be aligned in any given optical switch device. The optical alignment of individual waveguides is tedious and time-consuming. Waveguide arrays, including single rows of equidistantly spaced optical waveguides, can be used to simplify optical alignment. By way of example, Ducellier et al. in U.S. Pat. No. 6,487,334 disclose an optical switch using single-row optical fiber arrays and a concave mirror. Dual and even multiple optical switches can be constructed using multiple single-row fiber arrays disposed in a circle around the optical axis of the common concave mirror.
Detrimentally, in optical switches of Ducellier et al., individual and independent alignment of several waveguide arrays may be required, which increases device cost and reduces production yield. Accordingly, it is a goal of the invention to provide an optical switch, including a multicasting and/or a dual optical switch, in which only two waveguide arrays would need to be aligned.